[X86] Don't let LowerEXTRACT_SUBVECTOR call getNode for EXTRACT_SUBVECTOR.

This results in the simplifications inside of getNode running while we're legalizing nodes popped off the worklist during the final DAG combine. This basically makes a DAG combine like operation occur during this legalize step, but we don't handle something quite the same way. I think we don't recursively added the removed nodes to the DAG combiner worklist.

llvm-svn: 294929

1 files changed, 7 insertions, 5 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index cb002e44580..9d2b3fcd039 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -14010,12 +14010,14 @@ static SDValue LowerEXTRACT_SUBVECTOR(SDValue Op, const X86Subtarget &Subtarget,
           In.getSimpleValueType().is512BitVector()) &&
          "Can only extract from 256-bit or 512-bit vectors");
 
-  if (ResVT.is128BitVector())
-    return extract128BitVector(In, IdxVal, DAG, dl);
-  if (ResVT.is256BitVector())
-    return extract256BitVector(In, IdxVal, DAG, dl);
+  // If the input is a buildvector just emit a smaller one.
+  unsigned ElemsPerChunk = ResVT.getVectorNumElements();
+  if (In.getOpcode() == ISD::BUILD_VECTOR)
+    return DAG.getNode(ISD::BUILD_VECTOR, dl, ResVT,
+                       makeArrayRef(In->op_begin() + IdxVal, ElemsPerChunk));
 
-  llvm_unreachable("Unimplemented!");
+  // Everything else is legal.
+  return Op;
 }
 
 static bool areOnlyUsersOf(SDNode *N, ArrayRef<SDValue> ValidUsers) {